Visceral and post-Kala-Azar dermal leishmaniasis isolates show significant difference in their in vitro drug susceptibility pattern

Visceral leishmaniasis (VL) remains a major health problem in old world, and India accounts for half of the world burden. The widespread emergence of resistance to standard drug in India poses a major obstacle in the control of leishmaniasis. Post-Kala-Azar dermal leishmaniasis (PKDL) is considered as main source of drug resistance. Experimental data indicate that resistance against newer drugs is also imminent. Therefore, in vitro studies were carried out to test minimum parasiticidal concentration of five conventional and newly introduced anti-leishmanial drugs against 20 field isolates of Leishmania donovani obtained from visceral and post-Kala-Azar dermal leishmaniasis patients of India. Study revealed wide range of variation in minimum inhibitory concentration of sodium antimony gluconate (SAG). PKDL isolates displayed significantly lower susceptibility to SAG and miltefosine than VL isolates with P value of 0.0006 and 0.0243, respectively. All clinical isolates had higher IC₅₀ value for paromomycin and miltefosine as compared to reference strain indicating their vulnerability to develop unresponsiveness. However, isolates were uniformly susceptible to pentamidine and amphotericin B. The results of gene expression analysis of AQP1 were largely in agreement with phenotypic drug sensitivity results. Interestingly, significant down-regulation of AQP1 was observed in PKDL isolates as compared to VL isolates indicating their increased propensity for drug unresponsiveness. However, no significant difference in mRNA expression of LdMT and LdRos3 gene was found for two groups. The present study unravels valuable baseline scientific data showing variation in the drug susceptibility pattern in the L. donovani isolates. The information might have impact on the management and control of Indian visceral leishmaniasis.